1. Field of the Invention
The invention relates to a headrest support having a stay tube for receiving a headrest element, and to a method for producing a headrest support and a headrest having a headrest support.
2. Description of Related Art
Headrest supports are predominantly composed of U-shaped bent tubes, called stay tubes in the following, produced in most cases from band steel by welding, so that these have two limbs having free ends, and disposed between them, a connecting section which serves for receiving the headrest that is normally padded. The headrest can be fastened to the vehicle seat using the limbs of this stay tube that are extending out of the headrest, wherein the limbs are disposed in corresponding receptacles on the vehicle seat.
The stay tubes must conform to prescribed strength properties, so that they withstand the stresses that occur even in the case of a vehicle accident. However, the intensity of the stress varies over the length of the stay tube. Therefore, in the case of a crash, depending on the relative position of the headrest with respect to a vehicle seat, individual sub-areas of the stay tube are subjected to significantly higher stresses than those areas, which for instance, are disposed inside the vehicle seat. A design of the entire stay tube corresponding only to the greatest stress that occurs would guarantee a sufficient stability, however this would lead to a high material use which in turn would lead to high costs.
Furthermore, the stay tubes, in order for them to be usable as a headrest support, are subjected to a series of forming procedures which lead to a structural weakening of the stay tube, and therefore, to a reduction of the stability. In the case of a crash therefore, the formed areas represent particularly critical areas.
Among the forming procedures, in addition to producing bends, is the introduction of indentation marks on at least one limb of the stay tube, so that the headrest can be set in more than one position relative to the vehicle seat. The indentation marks can be formed, for instance, by recesses in the shape of notches, which are introduced into the stay tube and interact with latching means in the vehicle seat. Typically, multiple notches are made at offset distances on a limb, so that the headrest can be positioned at a variable distance to the vehicle seat.
The notches, which can be formed shallow, so that the notch base lies in the wall of the tube, as well as deep, so that the notch base lies deeper than the wall of the tube, as well as the other forming procedures, such as producing bends, lead to a structural weakening of the stay tube.
DE 10 2007 033 604 discloses a head rest support, which with minimized weight, satisfies the strength requirements of headrest supports, which are used particularly in motor vehicles. The tube wall of the stay tube has sections of different material thickness. Sections of greater material thickness are provided where high stresses are expected in the case of a crash, or where notches or recesses are to be installed. The sections of greater material thickness are created during rolling of the tube material for the stay tube. The notches, which are required for positioning the finished headrest on the seat, can be installed in the sections of greater material thickness.
Headrest supports, which have stay tubes having different wall thicknesses, and in which the recesses are installed at sections with greater material thickness, are lighter and stronger than conventional headrest supports. Under stress they deform significantly less than headrest supports that have a constant uniform wall thickness. However, it must be known before manufacturing the stay tube exactly where sections of greater material thickness are to be located. Furthermore, it must be guaranteed that the stay tubes are used exactly (bent, or are connected together) so that sufficient wall thickness is given where the highest stresses occur, or where a notch or other deformations are to be installed. Therefore, the necessary simplicity and flexibility during manufacturing is missing.
DE 197 34 712 discloses a tubular-shaped headrest support, which is reinforced using a wire section.